There are known checking systems and methods, for example in numerical control machine tools, for determining the position and/or the dimensions of machined workpieces by means of a contact detecting probe mounted in the machine that, in the course of a checking cycle, displaces with respect to the workpiece, touches the surfaces to be checked and responds to contact by wirelessly transmitting signals to a base station, typically located at a certain distance from the probe. The base station is in turn connected, by means of an interface device, to the numerical control unit that, by processing other signals indicative of the spatial position of the probe, obtains information about the position of the workpiece surfaces. The contact detecting probe can include electric batteries for the power supply of contact detecting circuits and devices for the wireless transmission that can occur, for example, by emitting electromagnetic signals of optical, or radio-frequency, type. As the probe is utilized just for short time intervals during the machining cycle of the associated machine tool, the associated detecting circuits and transmission devices are normally kept in a low power consumption “stand-by” state and powered-up only when there is the need to perform a checking cycle to optimize the life of the batteries. The probe activation, i.e. the switching from the “stand-by” state to the full powered-up state can take place by means of suitable switching devices located on the probe. These switching devices can be of the mechanical (microswitch) type, or remotely activated by means of activation signals, wirelessly transmitted from the base station. When the checking cycle ends, the probe circuits return to the low power consumption “stand-by” state either upon the wireless transmission of a suitable de-activation signal or, as an alternative, upon elapse of a predetermined time period. This time period can be calculated since the last useful signal transmitted from the probe in the course of the formerly mentioned cycle. In the event activation is implemented by means of a microswitch, de-activation is obviously implemented in a mechanical way.
Should there be a plurality of probes operating in a same working area, as frequently occurs, there can be foreseen a cycle for the selective activation of a selected probe, a cycle that foresees at first the activation of a plurality of probes and thereafter the selection further to a two-way exchange of identification and confirmation signals between the probes and the base station. Such a selective activation cycle is disclosed, for example, in U.S. Pat. No. 6,115,647.
In general, each probe is characterized by the value assumed by some parameters as, for example, those relating to the transmission frequency (more particularly in the case of radio-frequency transmission), to the activation mode (implemented in a mechanical way or by means of a wireless signal), to the signal that enables the identification of the probe (in the case of selective activation), to the operation/switching off time, and other parameters.
In the known systems, the values of the various parameters are defined and stored in the probe by programming devices with manually-operated switches (“dip-switches”), typically programmed at the time of installation of the probe in the associated machine.
The previously mentioned U.S. Pat. No. 6,115,647 illustrates and describes a similar device (more particularly, with reference to the reference number 29 in FIG. 2 and to the description in column 3, lines 57-61 and in column 4, lines 12-15).
This programming method is subject to some drawbacks. For example, should it be necessary to program many parameters, the number of manually-operated switches correspondingly increases and so problems in terms of layout dimensions are presented. These problems become quite significant also in consideration of the fact that market requirements call for ever smaller dimensions and frequently the operation for programming the switches, performed in a workshop environment, might accidentally dirty the switches and the nearby electronics.
In some systems including, for example, connections for the wireless transmission of signals of the optical type, there may be the need to program just one parameter, more specifically the interval of time whereafter the probe automatically switches off. In a similar case, the “dip-switch” located on the probe need not be provided and the time parameter can be programmed and stored in the probe in a “self-learning” phase. The “self-learning” phase includes the manually-operated activation of the probe in a specific way (for example by keeping the stylus deflected for a specified amount of time, or by mounting the battery with inverted polarity or in other ways that enable to differentiate the self-learning mode from the normal working mode), the subsequent de-activation, implemented in an analogous or reverse way or by a remote control transmitted from the base station, subsequently to a time interval either corresponding to the time that it is desirable to set as the switching off time, or in a known relationship (for example a multiple or a submultiple) with respect to said time, and the storing in the probe of the time interval, prior to suitable rounding off. This simple programming method is difficult or impossible to implement when it is necessary to set the values of more than one parameter or when such values are of other nature than a time interval.